Reland Auto-generate v8 version based on tags.

This relands the CL
https://codereview.chromium.org/797503007/.

It runs the version generation two times. First during
runhooks as a fallback for recipes that loose git context
(e.g. android_aosp). Second during compilation like in the
original CL. In case of failures, the result from the
runhooks call will be reused.

BUG=chromium:446166
LOG=n

Review URL: https://codereview.chromium.org/843913009

Cr-Commit-Position: refs/heads/master@{#26120}

.gitignore

@@ -27,6 +27,7 @@
 .project
 .pydevproject
 .settings
+.version.cc
 .*.sw?
 bsuite
 d8

BUILD.gn

@@ -314,6 +314,25 @@ action("run_mksnapshot") {
   }
 }
 
+action("generate_v8_version") {
+  visibility = [ ":*" ]  # Only targets in this file can depend on this.
+
+  script = "tools/push-to-trunk/generate_version.py"
+
+  sources = [
+    "src/version.cc",
+  ]
+
+  outputs = [
+    "$target_gen_dir/version.cc"
+  ]
+
+  args = [
+    rebase_path("$target_gen_dir/version.cc", root_build_dir),
+  ]
+}
+
+
 ###############################################################################
 # Source Sets (aka static libraries)
 #
@@ -398,6 +417,7 @@ source_set("v8_base") {
   visibility = [ ":*" ]  # Only targets in this file can depend on this.
 
   sources = [
+    "$target_gen_dir/version.cc",
     "src/accessors.cc",
     "src/accessors.h",
     "src/allocation.cc",
@@ -934,7 +954,6 @@ source_set("v8_base") {
     "src/v8threads.h",
     "src/variables.cc",
     "src/variables.h",
-    "src/version.cc",
     "src/version.h",
     "src/vm-state-inl.h",
     "src/vm-state.h",
@@ -1212,6 +1231,7 @@ source_set("v8_base") {
   defines = []
   deps = [
     ":v8_libbase",
+    ":generate_v8_version",
   ]
 
   if (is_win) {

DEPS

@@ -87,6 +87,13 @@ hooks = [
     'pattern': '.',
     'action': ['python', 'v8/tools/clang/scripts/update.py', '--if-needed'],
   },
+  {
+    # Generate v8 version based on the last git tag.
+    "pattern": ".",
+    "action": ["python",
+               "v8/tools/push-to-trunk/generate_version.py",
+               "--hook"],
+  },
   {
     # A change to a .gyp, .gypi, or to GYP itself should run the generator.
     "pattern": ".",

tools/gyp/v8.gyp

@@ -335,6 +335,34 @@
         }],
       ],
     },
+    {
+      'target_name': 'v8_version',
+      'type': 'none',
+      'conditions': [
+        ['want_separate_host_toolset==1', {
+          'toolsets': ['host'],
+        }, {
+          'toolsets': ['target'],
+        }],
+      ],
+      'actions': [
+        {
+          'action_name': 'generate_v8_version',
+          'inputs': [
+            '../../tools/push-to-trunk/generate_version.py',
+            '../../src/version.cc',
+          ],
+          'outputs': [
+            '<(SHARED_INTERMEDIATE_DIR)/version.cc',
+          ],
+          'action': [
+            'python',
+            '../../tools/push-to-trunk/generate_version.py',
+            '<(SHARED_INTERMEDIATE_DIR)/version.cc',
+          ],
+        },
+      ],
+    },
     {
       'target_name': 'v8_base',
       'type': 'static_library',
@@ -348,6 +376,7 @@
         '../..',
       ],
       'sources': [  ### gcmole(all) ###
+        '<(SHARED_INTERMEDIATE_DIR)/version.cc',
         '../../src/accessors.cc',
         '../../src/accessors.h',
         '../../src/allocation.cc',
@@ -887,7 +916,6 @@
         '../../src/variables.cc',
         '../../src/variables.h',
         '../../src/vector.h',
-        '../../src/version.cc',
         '../../src/version.h',
         '../../src/vm-state-inl.h',
         '../../src/vm-state.h',
@@ -899,8 +927,14 @@
       ],
       'conditions': [
         ['want_separate_host_toolset==1', {
+          'dependencies': [
+            'v8_version#host',
+          ],
           'toolsets': ['host', 'target'],
         }, {
+          'dependencies': [
+            'v8_version',
+          ],
           'toolsets': ['target'],
         }],
         ['v8_target_arch=="arm"', {

tools/push-to-trunk/generate_version.py

@@ -5,9 +5,23 @@
 
 """
 Script to set v8's version file to the version given by the latest tag.
+
+The script can be run in two modes:
+1) As a gclient hook with the option --hook.
+   The script will write a temporary version file into the checkout.
+2) During compilation as an action.
+   The script will write version.cc in the output folder based on the
+   tag info. In case of a failure it will fall back to the temporary file
+   from the hook call.
+
+In most cases, 2) will succeed and the temporary information from 1) won't
+be used. In case the checkout is copied somewhere and the git context is
+lost (e.g. on the android_aosp builder), the temporary file from 1) is
+required.
 """
 
 
+import optparse
 import os
 import re
 import subprocess
@@ -17,8 +31,10 @@ import sys
 CWD = os.path.abspath(
     os.path.dirname(os.path.dirname(os.path.dirname(__file__))))
 VERSION_CC = os.path.join(CWD, "src", "version.cc")
+TMP_VERSION_CC = os.path.join(CWD, ".version.cc")
 
-def main():
+
+def generate_version_file():
   tag = subprocess.check_output(
       "git describe --tags",
       shell=True,
@@ -50,28 +66,68 @@ def main():
     patch = "0"
 
   # Modify version.cc with the new values.
-  with open(VERSION_CC, "r") as f:
-    text = f.read()
   output = []
-  for line in text.split("\n"):
-    for definition, substitute in (
-        ("MAJOR_VERSION", major),
-        ("MINOR_VERSION", minor),
-        ("BUILD_NUMBER", build),
-        ("PATCH_LEVEL", patch),
-        ("IS_CANDIDATE_VERSION", candidate)):
-      if line.startswith("#define %s" % definition):
-        line =  re.sub("\d+$", substitute, line)
-    output.append(line)
-  with open(VERSION_CC, "w") as f:
-    f.write("\n".join(output))
-
-  # Log what was done.
+  with open(VERSION_CC, "r") as f:
+    for line in f:
+      for definition, substitute in (
+          ("MAJOR_VERSION", major),
+          ("MINOR_VERSION", minor),
+          ("BUILD_NUMBER", build),
+          ("PATCH_LEVEL", patch),
+          ("IS_CANDIDATE_VERSION", candidate)):
+        if line.startswith("#define %s" % definition):
+          line =  re.sub("\d+$", substitute, line)
+      output.append(line)
+  # Log what was calculated.
   candidate_txt = " (candidate)" if candidate == "1" else ""
   patch_txt = ".%s" % patch if patch != "0" else ""
   version_txt = ("%s.%s.%s%s%s" %
                  (major, minor, build, patch_txt, candidate_txt))
-  print "Modified version.cc. Set V8 version to %s" %  version_txt
+  print "Modifying version.cc. Set V8 version to %s" %  version_txt
+  return "".join(output)
+
+
+def delete_tmp_version_file():
+  # Make sure a subsequent call to this script doesn't use an outdated
+  # version file.
+  if os.path.exists(TMP_VERSION_CC):
+    os.remove(TMP_VERSION_CC)
+
+
+def main():
+  parser = optparse.OptionParser()
+  parser.add_option("--hook",
+                    help="Run as a gclient hook",
+                    default=False, action="store_true")
+  (options, args) = parser.parse_args()
+
+  if options.hook:
+    version_out = TMP_VERSION_CC
+  else:
+    if len(args) != 1:
+      print "Error: Specify the output file path for version.cc"
+      return 1
+    version_out = args[0]
+
+  assert os.path.exists(os.path.dirname(version_out))
+
+  try:
+    version_file_content = generate_version_file()
+  except Exception as e:
+    # Allow exceptions when run during compilation. E.g. there might be no git
+    # context availabe. When run as a gclient hook, generation must succeed.
+    if options.hook:
+      delete_tmp_version_file()
+      raise e
+    # Assume the script already ran as a hook.
+    print "No git context available. Using V8 version from hook."
+    assert os.path.exists(TMP_VERSION_CC)
+    with open(TMP_VERSION_CC, "r") as f:
+      version_file_content = f.read()
+
+  delete_tmp_version_file()
+  with open(version_out, "w") as f:
+    f.write(version_file_content)
   return 0
 
 if __name__ == "__main__":